The present invention relates to the preparation of para-menth-1-ene-7-sulfonate salts and more particularly to their preparation from the bicyclic terpene, .beta.-pinene.
Reactions of .alpha.-, and .beta.-pinene with various sulfur-containing compounds have been reported to lead to a diversity of products dissimilar in the terpene structure. For instance, Bordwell and Hewitt report that alpha-pinene and beta-pinene react with thioacetic acid under the influence of ultraviolet irradiation to give 3-pinanyl and 10-pinanyl thioacetate, respectively. The authors report that no para-menthene products could be found in the respective products. (Journal of American Chemical Society, Vol. 79, pages 3493-3496, 1957). Buess et al report that alpha-, and beta-pinene react with mercaptoacetic acid to give compounds of undetermined structure in the presence of peroxides and ultraviolet radiation (J. Org. Chem., Vol. 22, pages 197-200, 1957). Gaiffe and Castanet, however, report that alpha-, and beta-pinene do react with thioacetic acid and mercaptoacetic acid to produce para-menthene thioacetates and para-menthene mercaptoacetic acids, respectively, in the presence of di-t-butyl peroxide. These authors report similar results with mercaptoacetic acid, 2-hydroxyethane thiol, thiophenol, 2-mercapto-propionic acid, and methyl mercaptoacetate. (C. R. Acad. Soc. Paris, Vol. 271, Series C, pages 1012-1014, 1970). Further, Warner reports that .beta.-pinene will react with hydrogen sulfide to give a 10-pinanyl mercaptan (U.S. Pat. Nos. 3,114,776 and 3,248,315). It should be noted too that the reaction of a linear olefin with sodium bisulfite, for example often produces a mixture of the olefin sulfinate-sulfonate and the olefin sulfonate (eg. see Bright et al, J. Appl. Chem. Biotechnol., 25, pp. 901-912, 1975).
Certainly in view of the foregoing citations, reaction products of bicyclic terpenes, in general, and .beta.-pinene in particular, with sulfur-containing compounds cannot be predicted with certainty nor with accuracy. The present invention relates to para-menth-1-ene-7-sulfonate salts useful as surfactants and their corresponding para-menth-1-ene-7-sulfonic acids potentially useful as resolving agents, which sulfonate salts are prepared from beta-pinene.